Floating prestressed concrete wharf

ABSTRACT

A floating prestressed concrete wharf and a method of manufacturing the same are disclosed. The wharf includes pretensioned strands in critical disposition, may include transverse pretensioned cables in its uppermost slab, has wire reinforcing mesh in the concrete and a core of buoyant material.

United States Patent 9] Thomson [451 Mar. 26, 1974 FLOATING PRESTRESSEDCONCRETE WHARF [76] Inventor: Wade D. Thomson, P.O. Box 3288,

Jackson, Tenn. 38301 [22] Filed: May 7, 1973 211 Appl. No.: 357,909

521 US. Cl. 114/.5 F 51 Int. Cl B63b 35/00 58 Field of Search 114/.5 BD,.5 F, .5 T, 114/43.5, 61, 65 A, 66.5 F; 264/228; 61/5, ..6 1&8,.5Q

[56] References Cited UNITED STATES PATENTS 3,091,203 Usab l14/.5 F

2/1962 McCall ll4/.5 F 2/1967 Fulton ll4/.5 F

Primary Examiner-George E. A. Halvosa Assistant ExaminerCharles E.Frankfort Attorney, Agent, or Firm-J. Gibson Semmes [5 7] ABSTRACT Afloating prestressed concrete wharf and a method of manufacturing thesame are disclosed. The wharf includes pretensioned strands in criticaldisposition, may include transverse pretensioned cables in its uppermostslab, has wire reinforcing mesh in the concrete and a core of buoyantmaterial.

7 Claims, 9 Drawing Figures FLOATING PRESTRESSED CONCRETE WHARF FIELD OFTHE INVENTION This invention relates to the art of prestressed concretestructures, and more particularly to floating prestressed concretewharves which comprise cables pretensioned before the concrete is pouredinto the form for the wharf; and to the methods of making such,

DESCRIPTION OF THE PRIOR ART Prestressed and reinforced concrete wharfstructures of the floating and stationary types have been in use formany years. Similarly, the methods for making such structures havereceived considerable attention. U.S. Pat. No. 2,153,741 to Cobidiscloses a process for making prestressed hollow slabs; however, noteaching is found of the unique apparatus of the applicants inventionwherein both longitudinal and transverse pretensioning may beaccomplished. U.S. Pat. No. 2,518,091, to Stopkevyc, shows means forinterconnecting pontoon assemblies; however, no suggestion is made ofthe applicants connecting apparatus which provides either a flexible orrigid joint between wharf sections and a support for an optionalprotective deck plate over the joint. U.S. Pat. No. Re. 24,837 to Usabshows a reinforced concrete wharf structure made up of hollow,waterproof floats, but no disclosure is made of the applicants structurehaving pretensioned cables located critically in the overall structure.U.S. Pat. No. 3,022,759 to McCall shows a concrete floating wharf inwhich a longitudinally prestressed deck slab rests on hollow reinforcedconcrete floats. Applicants integral, prestressed structure having bothlongitudinal and transverse prestressed cables is neither shown norsuggested.

U.S. Pat. No. 3,073,271 to Brill discloses another means forinterconnecting float assemblies; but, as dis cussed above, no provisionis made for installation of a protective deck plate over the joint. U.S.Pat. No. 3,091,203 to Usab shows a concrete floating wharf structurehaving extensive wire mesh reinforcements and an elaboratepost-tensioning cable system. No suggestion of the applicantslongitudinal pretensioning system is made. U.S. Pat. No. 3,128,737 toUsab shows a reinforced concrete float having transverse cross rods forattachment of tie rails, but no mention is made of applicant's uniquetransverse pretensioned cables or wires which help retain threadedinserts used for attachment of side rails.

U.S. Pat. No. 3,207,829 to Nieber, et al. describes means and a methodfor pretensioning wires such as might be useful in practicing theinventive method disclosed herein; however, no teaching is found ofapplicants method of making a longitudinally and trans verselyprestressed wharf structure. U.S. Pat. No. 3,276,209 to Mosdelldiscloses the use of reinforcing rods in a floating wharf structure; butonce again, no mention is made of the applicant's structure wherein thefloat is prestressed as claimed herein. U.S. Pat. No. 3,323,479 to Filakshows a float structure having a buoyant core of lightweight material;however, no prestressed float structure is used.

U.S. Pat. No. 3,448,709 to Hardwick shows a float constructioncomprising lightweight floats and a reinforced deck slab. No suggestionis found of a unitary, prestressed structure as now disclosed. U.S. Pat.No. 3,5 80,202 to Thompson shows a wharf structure having reinforcingbars and wire mesh, and further including a lightweight core; but noprestressed structure is mentioned. U.S. Pat. No. 3,616,774 to Thompsonshows yet another floating dock structure which does not compriseprestressed concrete in the manner of this invention.

SUMMARY OF THE INVENTION The apparatus and method of this inventionprovide concrete floating wharf structure capable of being used ingreater overall length per unit than the known prior art devices, whileproviding a wharf that is resilient and flexible under in-serviceconditions. The increased wharf length permits the use of fewer units inassembling a wharf, thereby minimizing the number of connections to bemade between units and minimizing costs.

These advantages are embodied in the invention by providing a block oflightweight buoyant material such as expanded polystyrene, encased inwire reinforcing mesh, which acts as a temperature and shrinkagereinforcement for the concrete. The enclosed block is placed in a formof similar configuration having pretensioned cables strung along thelongitudinal corners thereof or as otherwise disposed. Preferablylightweight concrete is poured around the block in the form so as toencase the block, mesh and cables in an integral float or wharf unit.When the concrete has set, the cables are cut at the form and the formremoved, leaving a prestressed wharf unit, compressed under the actionof the cables or wires. If desired for greater flexibility, transversepretensioned cables may be provided within the top surface of the floatunit so as to provide prestressing in all directions in the upperportion of the unit, thereby increasing its resiliency and flexibility.Means are provided for joining one float unit to another and forattaching bumper rails along the longitudinal edges of the float units.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a perspective view of awharf unit according to the invention, partially cut away to'reveal theorientation of its components;

FIG. 2 shows an exploded perspective view of the components used tomanufacture the invention, exclusive of the concrete;

FIG. 3 shows a partial section through a longitudinal corner of theinvention, particularly the lightweight core, the pretensionedlongitudinal cable and the threaded inserts for the bumper rails;

FIG. 4 shows a side elevation in section taken along line 4-4 of FIG. 1;

FIG. 5 shows an elevation view of the means for connecting neighboringfloat units;

FIG. 6 shows a plan view of the means for connecting neighboring floatunits;

FIG. 7 shows a plan view-of the joint between neighboring float units,an optional cover plate being in place;

FIGS. 8 and 9 show alternate configurations for connecting the inventivefloat units.

DESCRIPTION OF THE PREFERRED EMBODIMENTS There follows a detaileddescription of the preferred embodiments of the invention, referencebeing had to the FIGURES in which like numerals identify like elementsof structure.

FIG. 1 shows a perspective view of a floating wharf unit, partially cutaway to reveal the interior structure of the unit. Unit comprises one ormore cores 12 of lightweight (density less than water) material such asexpanded polystyrene, which provide the necessary buoyancy for the unitwhen it is in place in the water as indicated by phantom water line 14.If desired hollow watertight enclosed volumes of similar configurationmay be used as cores. When two or more cores 12 are used, they arespaced so as to provide a membrane 16 of concrete therebetween, whichprovides lateral stability in the overall structure and prevents onecore from transmitting water to the next in the event that leakage intothe wharf unit should occur. The cores are preferably surrounded on allsides by a blanket 18 of lightweight concrete, which forms end wallmembranes 16 at either end. Embedded in the concrete adjacent to andsurrounding each core is a layer 20 of wire screening or mesh whichprovides reinforcement to strengthen the concrete against normalloading, temperature effects and shrinkage. Whereas lightweight concreteis specified, standard concrete may be applied as the blanket 18.

The cores 12 are preferably but not necessarily bevelled along theirlongitudinal corners 22 and 24, as shown, and further include a cutawayportion 26 in the longitudinal sides near the ends 28 and 30 of thewharf unit. See also FIG. 2. These bevelled portions provide alongitudinal space 32 within the concrete blanket 18 in which arelocated pretensioned cables 34, extending the entire length of the wharfunit. The size and number of the cables varies, depending on the lengthof the wharf unit. Attached to cables 34 along the upper longitudinaledges 36 and 38, are threaded inserts 40 which extend flush to the outerside surfaces of the unit. Bumpers 42 and 44, of wood, rubber or otherresilient material, are attached to the unit along edges 36 and 38 usingsuitable bolt fasteners 46 threaded into inserts 40. See also FIG. 3.The threaded inserts may also be installed flush to the upper surface toprovide attachment points for hand rails, and so forth. Where desired toprovide additional strength and flexibility in the upper portion ofblanket 18, transverse pretensioned wires or cables 48 may be includedwhich may be attached to each threaded insert as shown or merelystretched between the longitudinal pretensioned cables 34. The size ofthe wires varies depending on the width of the wharf unit.

Affixed to each end of the wharf unit 10 are combined end plates 50 and52, and connectors 54 and 56. These plates, which may be of galvanizedsteel, include on one side pairs of hooked anchor bars 58 and 60 whichextend into the concrete which fills the cutaway portions 26 of the endsof cores 12, thereby securely holding the end plates to the wharf unit.The cut ends 62 of cables 34 extend through apertures in the corners ofthe end plates. If desired, the end plates 50 and 52 may be secured byattaching gripping means to the ends of cables 34, in which case anchorbars 58 and 60 may be omitted; howeventhe use of anchor bars ispreferred. Attached to the end plates 50 and 52 are vertically disposedpairs of connector lugs 54 and 56 which are used to join individualwharf units in use. The upper and lower edges of end plates 50 and 52include out wardly projecting flanges 64 and 66. The top surface of thewharf unit 10 may be textured as desired to provide a safe walkingsurface as shown at 68.

FIG. 2 shows an exploded perspective view of the components used tomanufacture the wharf unit 10 in accordance with the method of theinvention. A form having inner dimensions of the size desired for thewharf units is assembled from a bottom plate 70, side plates 72 and 74and end plates 76 and 78. If desired, the side and end plates may behinged to bottom plate 70 so as to facilitate their set up and removalduring manufacture. Anysuitable means for securing the form togetherprior to insertion of the components of the wharf unit may be used, forexample, the side and end plates may be prewelded together.

End plates 50 and 52 are inserted into the form with anchor bars 58 and60 facing into the form. If desired, apertures 80 and 82 may be providedin end plates 76 and 78 to accommodate connectors 54 and 56; orconnectors 54 and 56 may be attached to end plates 50 and 52 after thewharf unit has been removed from the form. In any event, end plates 50and 52 must be secured in the form to prevent movement during pouring ofthe concrete. The cables 34 are then threaded through end plates 76 and78 and end plates 50 and 52, usually first at the bottom of the form,and then at the top. As the cables 34 are threaded through the top ofthe form, threaded fasteners 40 are strung thereon, one for eachattachment point desired for bumpers 42 and 44. At this point cores 12may be inserted into the forms after having been wrapped with layer 20of wire mesh. Cables 34 remain slack until this time, to facilitateinsertion of cores 12. Cables 34 are then pretensioned or stretchedusing hydraulic or mechanical tensioning means as are well known in theart. Cable chucks 84 or similar gripping means are affixed over the endsof cables 34 prior to tensioning and serve to hold the cables in thestretched position when the tensioning means (not shown) are removed.Threaded inserts 40 are pulled against the form side plates 72 and 74using bolts 86, which may be identical to fasteners 46.

If it is desired to provide transverse pretensioned cables or wires 48in the upper portion of blanket 18, these may now be threaded betweenthe threaded inserts 40 and pretensioned using any suitable means. Thecombined effects of the cables 34 and wire or cables 48 attached tothreaded insert 40 is thus to ensure that insert 40 cannot pull out ofthe wharf unit in service. Also at this time, it may be desirable toinstall sleeves through which lateral connecting rods 88 are passed.Rods 88 are threaded on each end in the upper and lower portions of themembranes l6, and are located in the spaces between the cores 12, underthe cables 48, and in similar locations in the end walls, to provideattachment points for wharf units attached side by side or end to side.See also FIGS. 8 and 9.

After the above preparations have been completed, the preferredlightweight concrete is poured into the form. This concrete is of suchconsistency that it will flow under the cores l2 and raise them untilthe lower portion of blanket 18 has flowed into place. To preventfurther upward movement of the cores 12 and to maintain them in theirproper position in the mold, it is sometimes necessary to fix the coresin place by any suitable means, especially if the transversepretensioned wires or cables 48 are not being used in the particularwharf unit. If the wires 48 are being used, they restrain the cores 12from excessive upward movement and thereby acquire some addedpretensioning. The form is filled carefully to avoid the inclusion ofany void spaces in blanket 18, after which the top surface may befinished or textured as desired depending on the intended use. Theconcrete is then permitted to set, the pretensioning cables are cutoutboard of end plates 50 and 52 and the form walls may be removed. Thecompleted wharf unit is then ready for attachmentof bumper rails 42 and44 and other connection fittings prior to being placed in the water.

FIG. 3 shows a partial section through a longitudinal corner of thewharf'unit. Concrete blanket 18 provides an essentially uniform coatingall around core 12. The upward force applied to transverse cable or wire48 has deformed it slightly as shown. The relationship of transversewire 48 and longitudinal cables 34 to the integral eye 90 of threadedinsert 40 is clearly shown.

FIG. 4 shows a side elevation in section taken along lines 4-4 ofFIG. 1. The spaces between the cores 12 form membranes l6. Lateralconnecting sleeve and rod elements 88, if used, extend through the upperportion of membrane 16 approximately on a level with threaded inserts40, and through the lower portion of membrane 16.

FIG. 5 shows an elevation view of the means for connecting neighboringfloats end-to-end. Connector lugs 54 and 56 are joined using long bolt92, threaded at either end, and fasteners 94. Both the top and bottompairs of lugs may be so joined, or only one, depending on the amount offlexure desired in the joint. To provide a suitable walkway over thejoint between wharf units 10, a cover plate 96, suitably textured forsafe walking, may be attached to flanges 64 and 66. FIG. 6 shows a planview of the connecting means without cover plate 96 and FIG. 7 shows theoptional cover plate in place.

FIGS. 8 and 9 suggest alternate means ofjoining one wharf unit toanother. In FIG. 8, lateral connecting rods 88 have been installedthrough sleeves, not shown, in the membranes 16 of a first wharf unit soas to extend from one side only thereof. See also FIG. 2. Affixed to theextending end of the connecting rods is a connecting plate identical toend plates 50 and 52 except for the anchor bars, having connecting lugssimilar to lugs 56 for connection to lugs 54 ofa second adjacent wharfunit to form a T structure. In FIG. 9, two wharf units similar to thefirst unit in FIG. 8 are joined side by side in like manner. These modesof joining one wharf unit to another are merely exemplary, and otherconfigurations will occur to one of ordinary skill in the art withoutdeparting from the spirit of this invention.

In practice, it has been found feasible to manufacture wharf units up to24 feet long, 4 feet wide and from 2 to 3 feet in depth. This comparesfavorably with prior art, non-prestressed units which typically areavailable in 8 foot lengths. The increased length made possible 6 bythis invention reduces the number of connections required for a giveninstallation, simplifies manufacture and reduces expense.

Having described my invention in such detail as to enable one skilled inthe art to make and use it, I claim:

1. A floating wharf unit of a rectangular parallelepiped configurationcomprising:

A. at least one core of light weight material B. a layer of concretesubstantially surrounding the at least one core to define a volumehaving top, bottom and sidewall surfaces; and

C. a first plurality of pretensioned strands of resilient material, afirst portion of the first plurality being located within the layer ofconcrete above the bottom surface of the unit along the bottomlongitudinal corners and a second portion of the first plural ity beinglocated within the layer of concrete below the upper surface of the unitalong the upper longitudinal corners, thereby maintaining the concretelayer in compression.

2. The wharf unit of claim 1 further comprising:

D. a layer of reinforcing wire mesh located in the concrete layer andsubstantially surrounding the at least one core.

3. The wharf unit of claim 1 further comprising:

D. a second plurality of pretensioned strands of resilient materialwithin the layer of concrete below the upper surface of the unit andtransverse to the second portion of the first plurality of pretensionedstrands, thereby maintaining the portion of the wharf unit below theupper surface in bilateral compression.

4. The wharf unit of claim 3 further comprising:

D. means attached to the second portion of the first plurality ofpretensioned strands below the top wall surface and extending to theside wall surface for attaching a bumper rail;

E. bumper rails extending along the longitudinal sides of the unit; and

F. means coacting with the attaching means for securing the bumper railto the wharf unit.

5. The wharf unit of claim 4 wherein the means for attaching a bumperrail comprises a plurality of threaded inserts each having an eyeintegral therewith, at least one of the second portion of the firstplurality of pretensioned strands being threaded through the eye of eachof the plurality of threaded inserts and the second plurality ofpretensioned strands of resilient material being stretched between theeyes of the plurality of inserts on opposite sides of the unit.

6. A floating wharf unit comprising:

A. at least one core of light weight material including longitudinalsides having cutaway portions at either end of the core,

B. a layer of concrete substantially surrounding the at least one coreto define a volume having top, bottom and sidewall surfaces; and

C. a first plurality of pretensioned strands of resilient material, afirst portion of the first plurality being located within the layer ofconcrete above the bottom surface of the unit and a second portion ofthe first plurality being located within the layer of concrete below theupper surface of the unit, thereby maintaining the concrete layer incompression,

D. means for joining one float to another comprising an end plate havingon one side a plurality of hookshaped anchor bars extending into theconcrete located in the cutaway portions and on the other side joiningone float to another further comprises hollow sleeves extending throughthe concrete membranes to the walls of the unit, the sleeves surroundingthreaded connecting rods.

1. A floating wharf unit of a rectangular parallelepiped configurationcomprising: A. at least one core of light weight material B. a layer ofconcrete substantially surrounding the at least one core to define avolume having top, bottom and sidewall surfaces; and C. a firstplurality of pretensioned strands of resilient material, a first portionof the first plurality being located within the layer of concrete abovethe bottom surface of the unit along the bottom longitudinal corners anda second portion of the first plurality being located within the layerof concrete below the upper surface of the unit along the upperlongitudinal corners, thereby maintaining the concrete layer incompression.
 2. The wharf unit of claim 1 further comprising: D. a layerof reinforcing wire mesh located in the concrete layer and substantiallysurrounding the at least one core.
 3. The wharf unit of claim 1 furthercomprising: D. a second plurality of pretensioned strands of resilientmaterial within the layer of concrete below the upper surface of theunit and transverse to the second portion of the first plurality ofpretensioned strands, thereby maintaining the portion of the wharf unitbelow the upper surface in bilateral compression.
 4. The wharf unit ofclaim 3 further comprising: D. means attached to the second portion ofthe first plurality of pretensioned strands below the top wall surfaceand extending to the side wall surface for attaching a bumper rail; E.bumper rails extending along the longitudinal sides of the unit; and F.means coacting with the attaching means for securing the bumper rail tothe wharf unit.
 5. The wharf unit of claim 4 wherein the means forattaching a bumper rail comprises a plurality of threaded inserts eachhaving an eye integral therewith, at least one of the second portion ofthe first plurality of pretensioned strands being threaded through theeye of each of the plurality of threaded inserts and the secondplurality of pretensioned strands of resilient material being stretchedbetween the eyes of the plurality of inserts on opposite sides of theunit.
 6. A floating wharf unit comprising: A. at least one core of liGhtweight material including longitudinal sides having cutaway portions ateither end of the core, B. a layer of concrete substantially surroundingthe at least one core to define a volume having top, bottom and sidewallsurfaces; and C. a first plurality of pretensioned strands of resilientmaterial, a first portion of the first plurality being located withinthe layer of concrete above the bottom surface of the unit and a secondportion of the first plurality being located within the layer ofconcrete below the upper surface of the unit, thereby maintaining theconcrete layer in compression, D. means for joining one float to anothercomprising an end plate having on one side a plurality of hook-shapedanchor bars extending into the concrete located in the cutaway portionsand on the other side a plurality of spaced connector lugs for joiningone float to another.
 7. The wharf unit of claim 6 wherein there are aplurality of cores of lightweight material separated by membranes ofconcrete and wherein the means for joining one float to another furthercomprises hollow sleeves extending through the concrete membranes to thewalls of the unit, the sleeves surrounding threaded connecting rods.